Storage library systems are often used by enterprises and the like to efficiently store and retrieve data from storage media. In the case of some storage libraries, the media are data cartridges (e.g., tape cartridges) that are typically stored and indexed within a set of magazines. When particular data is requested, a specialized robotic mechanism finds the appropriate cartridge, removes the cartridge from its magazine, and carries the cartridge to a drive that is designed to receive the cartridge and read its contents. Some storage libraries have multiple drives that can operate concurrently to perform input/output (IO) operations on multiple cartridges.
Operation of the robotic mechanism in the context of a data storage system typically involves a number of different location related tasks. For example, the robotic mechanism may be used for targeting of specific locations within the data storage system, for performing pick and place operations on media cartridges, for reading barcodes and/or other symbols or features, for auditing the existence and/or absence of media cartridges in magazines or drives, etc. Each of these and other operations can be frustrated when location-related errors are introduced into the environment if proper corrective feedback is not provided. For example, errors can easily be introduced into the system from physical jarring or manipulation of components, from compounding of errors inherent in electronic components, etc.
Some such operations can relate to auditing of inventory locations. For example, inventory locations can include media cartridge storing cells provided in a stacked arrangement (in a magazine) for convenient storage of large numbers of media cartridges. Performing a tape audit in a storage library system can involve distinguishing between unlabeled cartridges or magazines (or errors in the detection system) and empty cell or magazine locations. Some conventional systems perform such audits by either having the robotically actuated hand assembly reach into cells or other locations mechanically to sense whether a cartridge or magazine is present, or by using the robot to read barcodes or other labels. Extending the robotically actuated hand assembly into many locations for auditing purposes can add significant delay to the audit time, and reading labels can add cost and error (and often complex calibration processes).